In the prior art are known the cutting units of hydro-mechanical slot perforating machines, which include cutting tools enabling to form simultaneously two perforation slots in the production string, with the mechanism of their extension, for example, disclosed in patents RU 2249678 C2, IPC E21B 43/112, 10.04.2005, RU 2302515 C2, IPC E21B 43/112, 10.07.2007, RU 2348797 C1, IPC E21B 43/112, 10.03.2009. These analogs include cutting tools in the form of two cutting discs mounted on the axis in the balance beam shoulders, or in the form of two cutters, or in the form of two cutting edges of the rotary knife. Thus, the analogs use only two cutting tools, diametrically oriented, each of which performs a perforation slot from its side. The speed of slots formation in each projection is relatively low.
It is obvious that the speed of perforation slot formation in the column may be increased if not one but multiple cutting tools will be simultaneously involved in the process of its formation. The productivity of the cutting unit will increase in the number of times depending on the quantity of cutting tools which will be involved in the work.
There are multi-sectional cutting units of slot-type perforating machines involving several sections or working cylinders containing one or two cutting tools: RU 2371569 C1, IPC 21B 43/112, 27.10.2009, RU 86654 U1, IPC E21B 43/112, 10.09.2009, RU 2389867 C1, IPC E21B 43/112, 20.05.2010. Such devices, in the case if orientation of the cutting tools of several sections (working cylinders) is in one projection, may be used to accelerate the formation of perforating slots.
However, the disadvantage of multiple-cutting units is the application of cutting tools extension mechanisms, suggesting the presence of a significant distance between the cutting tools in working position.
For example, if the cutting tools of different sections have orientation so that some of them are located in one projection, and some—are located in another, we get a double-sided cutting unit with several working tools on each side. However, the large distance between the cutting tools will lead to the fact that they will work on segments of the perforation interval, only partially overlapping, so the segments of perforating slots formed at the same time will have a significant height difference. This will lead to uneven opening of the column and to uneven wear of cutting tools, as well as to the possibility of unwanted disclosure of the column outside of the perforation interval.
In addition, the utilization of the known extension mechanisms of cutting tools in multi-sectional cutter units, especially those where the section contains only one cutting tool, results in increase of perforators size, making them too long, cumbersome, affects the performance of the perforators.
The above drawbacks complicate the use of perforators with multi-sectional cutting units for the purpose of acceleration of perforating slots formation.
The objective of the proposed invention is to create a design of slot-type perforator cutting unit, which is more compact in size and provides more uniform opening of the production column with the simultaneous acceleration of the formation of at least two perforation slots of sufficient depth.
The closest cutting unit to the invention is herein referred to as a ‘prototype’, which is a hydro mechanical slot-type perforator cutting unit as per a Russian Federation Patent for Utility Model RU 100802 U1, IPC E21B 43/112, 27.12.2010.
The cutting unit of a hydro mechanical slot-type perforator of the prototype includes telescoping blades mounted on the axes of the upper and lower holders, which are set inside the perforator's case by means of the fingers, while the upper holder is mounted on the plunger and the lower holder is secured to the casing, in addition, holders are made flat and located in the same plane with the possibility of deviations in opposite directions during translational impact of the plunger, in addition, working surfaces of the holders interacting with each other are mounted at the ends of the holders, rounded, and the lower holder is additionally provided with a supporting surface with the possibility of exposure to the lower spring anchor through the washer, while the lower spring is located in the glass—the tensioner. The diameter of the cutting disks used in the construction of the cutting unit in the prototype is close to the diameter of the perforator's casing that allows creating perforations slots of a considerable depth.
The disadvantage of the cutting unit according to the prototype is the possibility of the inclusion of only two cutting disks—one disk for each of two projections of the perforation slots forming that does not accelerate opening of the column. This is due to the construction of the extension mechanism of cutting tools, consisting of two coupled holders.
The lack of a mechanism to bring the cutting unit in the transport position and fix it in this position before and after perforation can also be attributed to the disadvantages of the prototype.